Once the decals have dried, I painted black in between them to hide the "seams" in between each of them.
Next, I masked the console, except for the decaled area, and sprayed some glossy clear-coat, just to seal that area.

Now, the control panels can be painted with Tamiya clear acrylic colors as shown.
I wanted some blue in there too, and I used Testors' blue metallic. That worked nicely too.

You can see how the overall effect is iridescent. It's quite effective.